The present invention relates to a positive type photosensitive polyimide precursor composition where regions exposed using ultraviolet radiation dissolve in aqueous alkali solution and which is suitable for semiconductor element surface protective films, layer insulation films and the like. That is to say, it relates to a positive type photosensitive polyimide precursor composition suitable for semiconductor element surface protective films, layer insulation films and the like, where regions exposed using ultraviolet radiation dissolve in aqueous alkali solution.
As examples of positive type heat-resistant resin precursor compositions where the exposed regions are dissolved by developing, there are known those where a naphthoquinone diazide is added to a polyamic acid (JP-A-52-13315), those where a naphthoquinone diazide is added to a soluble polyimide which possesses hydroxyl groups (JP-A-64-60630) and those where a naphthoquinone diazide is added to a polyamide which possesses hydroxyl groups (JP-A-56-27140).
However, where a naphthoquinone diazide is added to an ordinary polyamic acid there is the problem that, since the solubility of the polyamic acid carboxyl groups is higher than the inhibitory effect of the naphthoquinone diazide in terms of alkali solubility, in most cases the desired pattern cannot be obtained. Furthermore, where a hydroxyl group-containing soluble polyimide resin is added, although there is little such aforesaid problem, there is the difficulty that, in order to provide solubility, the structures are limited and the solvent resistance of the polyimide resin obtained is poor.
Taking into account the aforesaid shortcomings, in the present invention it has been discovered that by adding a novel naphthoquinone diazide compound of specified structure to a polyimide precursor, the resin composition obtained essentially does not dissolve at all in alkali developer prior to exposure but, once exposed, it readily dissolves in the alkali developer, so there is little film loss due to the developing and developing is possible in a short time. It is on this discovery that the present invention is based.
That is to say, in accordance with the present invention, by adding a specified naphthoquinone diazide compound to a polyimide precursor of specified structure, there can be provided a positive type heat-resistant resin composition which shows little film loss in the unexposed regions due to developing and, furthermore, which can be developed in a short time.
The present invention relates to a positive type photosensitive resin precursor composition which is characterized in that it contains polymer having, as its chief component, structural units represented by the following general formula (1) and, furthermore, in that it satisfies the following conditions (a) and/or (b).
(a) There is included an ester of a naphthoquinone diazide sulphonic acid and a phenol compound of dipole moment 0.1 to 1.6 debye
(b) There is included a phenol compound represented by general formula (8) and a naphthoquinone diazide sulphonic acid and/or an ester of a phenol compound represented by general formula (8) and a naphthoquinone diazide sulphonic acid 
(In general formula (1), R1 represents a bivalent to octavalent organic group with at least two carbon atoms, R2 represents a bivalent to hexavalent organic group with at least two carbon atoms, and R3 represents hydrogen or an organic group with from one to ten carbons. n is an integer in the range 10 to 100,000, m is an integer in the range 0 to 2, and p and q are integers in the range 0 to 4. However, p and q are not simultaneously 0.) 
(In the formula, R10, R11, R13 and R14 each represents a hydrogen atom or a C1-8 alkyl group, alkoxy group, carboxyl group or ester group. R12 represents a hydroxyl group, hydrogen atom or C1-8 alkyl group. xcex1, xcex2o and xcex4 represent integers in the range 0 to 3. However, xcex1+xcex2xe2x89xa65, xcex2+xcex4xe2x89xa75 and xcex1+xcex2 greater than 0. x represents an integer in the range 1 to 3.)
Optimum Form for Practising the Invention
In the present invention, the polymer having, as its chief component, structural units represented by general formula (1) is a polymer from which there can be formed, by heating or by means of a suitable catalyst, polymer having imide rings, oxazole rings or other cyclic structures. By forming cyclic structures, the heat resistance and solvent resistance are markedly raised.
Aforesaid general formula (1) represents a hydroxyl group-containing polyamic acid or a polyhydroxyamide and, due to the presence of the hydroxyl groups, the solubility in aqueous alkali solution is better than that of a polyamic acid which does not possess hydroxyl groups. In particular, phenolic hydroxyl groups are the preferred hydroxyl groups in terms of the solubility in aqueous alkali solution. Moreover, by having at least 10 wt % of fluorine atoms in general formula (1), a suitable degree of water repellency is shown at the film interface at the time of the developing with aqueous alkali solution, so permeation at the interface, etc, is suppressed. However, if the fluorine atom content exceeds 20 wt %, the solubility in the aqueous alkali solution is lowered, the organic solvent resistance of the polymer which has been provided with cyclic structures by heat treatment is reduced, and the solubility in fuming nitric acid declines, so this is undesirable. Thus, a fluorine atom content of 10 wt % to 20 wt % is preferred.
In the case where m is 0, hydroxyphthalic acid, bis(hydroxycarboxyphenyl)hexafluoropropane or oxydi(hydroxycarboxybenzene), etc, may be used.
In aforesaid general formula (1), R1(OH)p(COOR3)m denotes the acid structural component and it is preferred that this group be a bivalent to octavalent group with at least two carbons, which contains an aromatic ring and possesses from 1 to 4 hydroxyl groups.
Specifically, a group having a structure as represented by general formula (2) is preferred. In this case, R4 and R6 represent C2-20 trivalent or tetravalent organic groups. In particular, groups containing an aromatic ring are preferred in terms of the heat resistance of the polymer obtained, with particularly preferred examples thereof being the trimellitic acid residue, the trimesic acid residue and the naphthalene tricarboxylic acid residue. 
R5 is preferably a hydroxyl group-containing C3-20 trivalent to hexavalent organic group. In addition, it is preferred that the hydroxyl groups be positioned adjacent to an amide bond. Examples thereof are groups with bonded amino groups such as the bis(3-amino-4-hydroxyphenyl)hexafluoropropane residue and the bis(3-hydroxy-4-aminophenyl)hexafluoropropane residue, which contain fluorine atoms, and the bis(3-amino-4-hydroxyphenyl)propane residue, the bis(3-hydroxy-4-aminophenyl)propane residue, the 3,3xe2x80x2-diamino-4,4xe2x80x2-dihydroxybiphenyl residue, the 3,3xe2x80x2-diamino-4,4xe2x80x2-dihydroxybiphenyl residue, the 2,4-diaminophenol residue, the 2,5-diaminophenol residue and the 1,4-diamino-2,5-dihydroxybenzene residue, which do not contain fluorine atoms.
R7 and R8 in general formula (2) may each be hydrogen or a C1-10 organic group. If there are more than 10 carbons, the solubility in the alkali developer is lowered. R7 and R8 may be the same or different. o and s denote 1 or 2, and r denotes an integer in the range 1 to 4. If r is 5 or more, then the properties of the heat-resistant film obtained decline and the water absorption becomes considerable.
Amongst the compounds of general formula (2), those of structure as shown below may be given as preferred examples, but there is no restriction thereto. 
In the case where q in the R2(OH)q moiety of general formula (1) is 1 or more, there can employed a dicarboxylic acid residue, tetracarboxylic acid residue or tricarboxylic acid residue which does not contain hydroxyl groups. As examples thereof, there are the isophthalic acid residue, terephthalic acid residue, dicarboxydiphenyl ether residue, dicarboxydiphenyl sulphone residue, bis(carboxyphenyl)hexafluoropropane residue, naphthalenedicarboxylic acid residue, pyromellitic acid residue, benzophenonetetracarboxylic acid residue, bisphenyltetracarboxylic acid residue, diphenyl ether tetracarboxylic acid residue, diphenyl sulphone tetracarboxylic acid residue and other such aromatic tetracarboxylic acid residues, or the diester compounds where two of these carboxyl groups are given methyl or ethyl groups, the butanetetracarboxylic acid residue, dicyclopentanetetracarboxylic acid residue or other such aliphatic tetracarboxylic acid residues, or the diester compounds thereof where two of these carboxyl groups are given methyl or ethyl groups, the trimellitic acid residue, the trimesic acid residue and other such aromatic tricarboxylic acid residues, and the like.
R2(OH)q in general formula (1) denotes the diamine structural component. With regard to preferred examples thereof, it is desirable in terms of the heat resistance of the polymer obtained that R2(OH)q contains aromaticity and it is also desirable that it possesses hydroxyl groups. Specific examples are the bis(amino-hydroxy-phenyl)hexafluoropropane residue, which contains fluorine atoms, and the diaminodihydroxypyrimidine residue, diaminodihydroxypyridine residue, hydroxy-diamino-pyrimidine residue, diaminophenol residue and dihydroxybenzidine residue, which do not contain fluorine atoms, and also those of structure represented by general formulae (3), (4) and (5). 
In general formula (3), R9 and R11 represent C2-20 trivalent or tetravalent organic groups which contain hydroxyl groups, and from the point of view of the heat resistance of the polymer obtained it is preferred that they contain an aromatic ring. Specific examples are the groups represented by the following formulae. 
i represents an integer in the range 1 to 4, j and k represent integers in the range 0 to 4, and j+k is at least 1. Furthermore, there can be used aliphatic groups such as the hydroxycyclohexyl group or dihydroxycyclohexyl group.
R10 in general formula (3) represents a C2-30 bivalent organic group. From the point of view of the heat resistance of the polymer obtained, it should be a bivalent group possessing aromaticity, examples of which are the following. 
In general formula (4), R12 and R14 represent C2-30 bivalent organic groups. In terms of the heat resistance of the polymer obtained, they should be bivalent groups with aromaticity, as examples of which there can be cited the same groups as provided above as specific examples of R11 in general formula (3). R13 represents a hydroxyl group-containing C2-20 trivalent to hexavalent organic group, and in terms of the heat resistance of the polymer obtained it is preferred that it be a group with an aromatic ring. As examples of such groups, there can be cited the same groups as provided above as specific examples of R9 and R11 in general formula (3).
In general formula (5), R15 represents a C2-20 bivalent organic group. In terms of the heat resistance of the polymer obtained, it should be a bivalent group which possesses aromaticity, as examples of which there can be cited the same groups as provided above as specific examples of R10 in general formula (3). R16 in general formula (5) represents a hydroxyl group-containing C2-20 trivalent to hexavalent organic group and, in terms of the heat resistance of the polymer obtained, a group with an aromatic ring is preferred. As examples of such groups, there can be cited the same groups as provided above as specific examples of R9 and R11 in general formula (3). Specific examples of the groups represented by general formula (3) are the following. 
Specific examples of the groups represented by general formula (4) are the following. 
Specific examples of the groups represented by general formula (5) are the following. 
Furthermore, when p in R1(OH)p(COOR3)m of general formula (1) is from 1 to 4, it is possible to use a diamine component which does not have hydroxyl groups. Examples in such circumstances are the following. 
R3 in general formula (1) represents hydrogen or an organic group with from 1 to 10 carbons. From the point of view of the stability of the photosensitive resin precursor solution obtained, R3 is preferably an organic group, but in terms of the solubility in aqueous alkali solution hydrogen is preferred. In the present invention it is possible to use a mixture of a hydrogen atom and alkyl group. By controlling the amount of hydrogen and organic group employed as R3, the solubility rate in the aqueous alkali solution can be made to vary, so by adjustment thereof it is possible to obtain a photosensitive resin precursor solution having a suitable rate of dissolution. R3 may be all hydrogen or it may be all organic group, but it is preferred that R3 be from 10% to 90% hydrogen. If the number of carbons in R3 exceeds 10, the aqueous alkali solubility is lost.
Furthermore, in order to enhance the adhesion to the substrate, there may be copolymerized aliphatic groups with a siloxane structure as R1(OH)p(COOR3)m or as R2(OH)q in general formula (1), within a range that does not lower the heat resistance. Specifically, there can be copolymerized from 1 to 20 mol % of the following as R1(OH)p(COOR3)m. 
(R represents a hydrogen atom or a C1-10 monovalent organic group.)
In the case of the R2(OH)q moiety in general formula (1), there can be copolymerized from 1 to 20 mol % of the bis(3-aminopropyl)tetramethyldisiloxane residue, the bis(4-aminophenyl)octamethylpentasiloxane residue, the xcex1,xcfx89-bis(3-aminopropyl)permethylpolysiloxane residue or the like.
The polymer of the present invention may comprise only structural units represented by general formula (1) or it may also be a copolymer or a blend with other structural units. In such circumstances, it is preferred that there be present at least 90 mol % of the structural units represented by general formula (1). The type and the amount of other structural units incorporated by copolymerisation or by blending will preferably be. selected such that there is no impairment of the heat resistance of the polyimide polymer obtained by the final heat treatment.
As examples of the synthesis of the photosensitive resin precursor composition of the present invention, there can be employed the method of reacting a tetracarboxylic acid dianhydride and a diamine compound at low temperature (C. E. Sroog et al, Journal Polymer Science, Part A-3, 1373 (1965)), the method in which a diester is obtained between a tetracarboxylic acid dianhydride and an alcohol, after which reaction is performed with an amine in the presence of a condensing agent (JP-A-61-72022) and the method in which a diester is obtained between a tetracarboxylic acid dianhydride and an alcohol, after which the remaining dicarboxylic acid is converted to the acid chloride form and then reaction performed with an amine (JP-A-55-30207).
In the present invention, the naphthoquinone diazide compound added is a compound obtained by the reaction of naphthoquinone diazide sulphonic acid with a phenol compound of dipole moment 0.1 to 1.6. In the present invention, the dipole moment of the phenol compound can be determined by molecular orbital calculation. Using a Dell notebook type personal computer, model Latitude CP, provided with 64 MB of memory, the molecular structure was input with the Cambridge Co. molecular modelling software xe2x80x9cChem3Dxe2x80x9d and, after stabilizing the structure by means of a molecular strength of field calculation based on the MM2 parameter accompanying said software, the optimum structure was calculated by the parameter AM-1 method using MOPAC-97 accompanying said software. The dipole moment at this time was employed.
By using a phenol compound of small such dipole moment, the hydrophobic character of the naphthoquinone diazide sulphonic acid ester obtained is raised. Hence, the unexposed regions hardly dissolve at all in aqueous alkali solution. Moreover, in the exposed regions, since an indene carboxylic acid residue is produced by the photodecomposition of the naphthoquinone diazide group, the solubility in aqueous alkali solution is raised. Hence, it is possible to obtain an excellent pattern with little film loss in the unexposed regions due to development.
If the dipole moment is greater than 1.6 debye, then there is little protective effect in the unexposed regions, while if it is less than 0.1 debye the naphthoquinone diazide sulphonic acid ester formed from said compound is no longer highly compatible with the polymer of general formula (1), so it is no longer possible to obtain an excellent image. For such reasons, the dipole moment preferably lies in the range 0.1 to 1.6 debye, more preferably 0.15 to 1.3 debye and still more preferably in the range 0.2 to 1 debye.
Again, it is better if the phenol compound of dipole moment from 0.1 to 1.6 debye has at least two benzene rings. Where there is one benzene ring, the effect in terms of suppressing the solubility in aqueous alkali is small, so there is a fear that the specified performance will not be realized. On the other hand, however, if there are 10 or more benzene rings, problems arise such as the compatibility with the polymer being poor, there being incomplete decomposition in the heat treatment after the pattern is obtained, and the properties of the film being impaired. Hence, the preferred phenol compound in the present invention will have a form in which there are from 1 to 10 benzene rings, and more preferably from 3 to 6 benzene rings. As the photosensitive agents represented by general formulae (6) and (7) in the present invention, there may be employed compounds with one type of structure or there may be used a mixture of a number of compounds of different structures. In the case where a plurality of such compounds is used, it is preferred that the average dipole moment of the phenol compound in the photosensitive agent used be no more than 1.5 debye. 
(X represents an oxygen atom or sulphur atom. R4 and R5 each represent a hydrogen atom or a C1-10 monovalent organic group, and they may both be the same or different. r and s represent integers in the range 0 to 4.) 
In general formula (6), R17 and R18 each represent a hydrogen atom or a C1-10 monovalent organic group. Using a group with no more than 2 carbons is preferred in terms of the excellence of the film heat resistance after heat treatment. From this point of view, using hydrogen atoms is further preferred. y and z denote integers in the range 0 to 4. From the point of view of the coloration following heat treatment, a value of 2 or below is preferred. X represent an oxygen atom or sulphur atom but oxygen is preferred in terms of the atom dipole moment being small and the heat resistance being good.
For R19, R20, R21 and R22 in general formula (7), there can be used the same groups as for R17 and R18 in general formula (6) above. xcex1, xcex2, "khgr" and xcex4 are the same as y and z in general formula (6).
By adding a compound of such structure, it is possible to markedly lower the film loss from the unexposed regions due to development and it is possible to obtain an excellent pattern in a short development time. In one of the quinone diazide compounds represented by general formula (7), when the hydrogen atoms denoted by Q are increased, there is an increase in the solubility, in alkali developer, of the photosensitive agent represented by general formula (7), so the effect in terms of protecting the polymer represented by general formula (1) is reduced. From this point of view, the proportion comprising hydrogen atoms is preferably no more than ⅓ and more preferably no more than ⅕. Again, as examples of the groups in cases where these are other than hydrogen atoms, there are the 4-naphthoquinone diazide sulphonyl group or the 5-naphthoquinone diazide sulphonyl group shown below. 
The 4-naphthoquinone diazide sulphonyl group absorbs in the i-line region of a mercury lamp and is suitable for i-line exposure, while with the 5-naphthoquinone diazide sulphonyl group absorption extends to the g-line region of a mercury lamp and it is suitable for g-line exposure. In the present invention, there can be favourably used both the 4-naphthoquinone diazide sulphonyl group and the 5-naphthoquinone diazide sulphonyl group, and it is preferred that selection between the 4-naphthoquinone diazide sulphonyl group and the 5-naphthoquinone diazide sulphonyl group be made depending on the exposure wavelength. Again, it is also possible to jointly introduce both the 4-naphthoquinone diazide sulphonyl group and the 5-naphthoquinone diazide sulphonyl group into the same molecule, or there can be used a mixture of a photosensitive agent in which the 4-naphthoquinone diazide sulphonyl group has been introduced as a photosensitive group and a photosensitive agent in which the 5-naphthoquinone diazide sulphonyl group has been introduced as a photosensitive group.
As examples of the compounds with a phenolic hydroxyl group represented by general formula (8) in the present invention, there are BisRS-2P, BisPG-26X, BisRS-3P, BisOC-OCHP, BisPC-OCHP, Bis25X-OCHP, Bis26X-OCHP, BisOCHP-OC, Bis236T-OCHP, methylenetris-FR-CR, BisRS-26X and BisRS-OCHP (the above are commercial names of products manufactured by the Honshu Chemical Industry Co.), and BIR-OC, BIP-PC, BIR-PC, BIR-PTBP, BIR-PCHP, BIP-BIOC-F, 4PC, BIR-BIPC-F and TEP-BIP-A (the above are commercial names of products manufactured by the Asahi Organic Chemicals Industry Co.). 
R23 and R24 preferably represent a methyl group or hydrogen atom. It is preferred that at least one R25 be a hydroxyl group, while otherwise R25 represents a hydrogen atom, methyl group, tert-butyl group, cyclohexyl group or hydroxybenzyl group. Furthermore, R26 and R27 preferably represent a hydroxyl group, hydrogen atom or cyclohexyl group. It is undesirable that R23, R24, R25 and R26 be groups other than as described above, in that instead of an alkali solubility promoting effect, they will have a considerable effect in impeding dissolution. Further preferred examples of the compound with a phenolic hydroxyl group are BisRS-2P, BisRS-3P, BisP-OCHP, methylenetris-FR-CR, BisRS-26X, BIP-PC, BIR-PC and BIR-BIPC-F. By adding such a compound which possesses a phenolic hydroxyl group, the resin composition obtained essentially does not dissolve in the alkali developer before exposure, but following exposure it readily dissolves in alkali, so there is little film loss by the development and developing is easy in a short time.
The amount of such compound with a phenolic hydroxyl group added is preferably from 1 to 50 parts by weight, and more preferably 3 to 40 parts by weight, per 100 parts by weight of the polymer.
The naphthoquinone diazide compound added in the present invention is preferably a compound in which a naphthoquinone diazide sulphonic acid is coupled to the compound with a phenolic hydroxyl group by esterification. The compound with a phenolic hydroxyl group employed for this purpose may be the same as the compound with a phenolic hydroxyl group represented. by general formula (8) employed in the present invention, or it may be different. As examples of such compounds which are not represented by general formula. (8), there are compounds like naphthol, tetrahydroxybenzophenone, methyl gallate, bisphenol A, methylenebisphenol, TrisP-HAP (commercial name, made by the Honshu Chemical Industry Co.), BisP-AP (commercial name, made by the Honshu Chemical Industry Co.), with preferred examples of the aforesaid naphthoquinone diazide compound being formed by esterification of these with 4-naphthoquinone diazide sulphonic acid or 5-naphthoquinone diazide sulphonic acid. However, other compounds can also be used.
Furthermore, the naphthoquinone diazide compounds conforming to general formula (9) are also preferred in the present invention. 
(In the formula, R27, R28, R30 and R31 each represent a hydrogen atom, or a C1-8 alkyl group, alkoxy group, carboxyl group or ester group. At least one R29 denotes xe2x80x94OQ (the naphthoquinone diazide sulphonyl group), while the rest represent hydroxyl groups, hydrogen atoms or C1-8 alkyl groups. a and b represent integers in the range 0 to 3, and Q represents the 5-naphthoquinone diazide sulphonyl group or the 4-naphthoquinone diazide sulphonyl group)
For example, there are the 5-naphthoquinone diazide sulphonyl ester compounds or the 4-naphthoquinone diazide sulphonyl ester compounds of compounds with a phenolic hydroxyl group such as BisRS-2P, BisPG-26X, BisOC-OCHP, BisP-OCHP, BisPC-OCHP, Bis25X-OCHP, Bis26X-OCHP, BisOCHP-OC, Bis236T-OCHP, methylenetris-FR-CR, BisRS-26X and BisRS-OCHP (the above are commercial names of products manufactured by the Honshu Chemical Industry Co.), and BIR-OC, BIP-PC, BIR-PC, BIR-PTBP, BIR-PCHP, BIP-BIOC-F, 4PC, and BIR-BIPC-F (the above are commercial names of products manufactured by the Asahi Organic Chemicals Industry Co.). Amongst these, R27 and R28 are preferably a methyl group or hydrogen atom. At least one R29 preferably denotes xe2x80x94OQ (the naphthoquinone diazide sulphonyl group), while the rest represent hydroxyl groups, hydrogen atoms, methyl groups, tert-butyl groups or cyclohexyl groups. Again, R30 and R31 are preferably a hydroxyl group, hydrogen atom or cyclohexyl group. In the case where R27, R28, R30 and R31 are respectively other than as described above, following exposure of the naphthoquinone diazide compound, when dissolving in the alkali developer, there is a considerable dissolution inhibition effect by the substituent groups, so there is a lowering of the sensitivity, which is undesirable. As further preferred examples of the 5-naphthoquinone diazide sulphonyl ester compounds or the 4-naphthoquinone diazide sulphonyl ester compounds of the compounds with a phenolic hydroxyl group, there are the 5-naphthoquinone diazide sulphonyl esters and the 4-naphthoquinone diazide sulphonyl esters of BisRS-2P, BisP-OCHP, BisRS-OCHP, methylenetris-FR-CR, BisOCHP-OC, BIP-PC, BIR-PC and BIR-BIPC-F.
The 4-naphthoquinone diazide sulphonyl esters exhibit absorption in the i-line region of a mercury lamp and are suitable for i-line exposure, while with the 5-naphthoquinone diazide sulphonyl esters absorption extends to the g-line region of a mercury lamp and they are suitable for g-line exposure. In the present invention, there can be favourably used both the 4-naphthoquinone diazide sulphonyl group and the 5-naphthoquinone diazide sulphonyl group, and it is preferred that selection be made between the 4-naphthoquinone diazide sulphonyl group and the 5-naphthoquinone diazide sulphonyl group depending on the exposure wavelength. Again, it is also possible to obtain a naphthoquinone diazide sulphonyl ester compound jointly using the 4-naphthoquinone diazide sulphonyl group and the 5-naphthoquinone diazide sulphonyl group in the same molecule, or there can be used a mixture of the 4-naphthoquinone diazide sulphonyl ester compound and the 5-naphthoquinone diazide sulphonyl ester compound.
The naphthoquinone diazide compound of the present invention can be synthesized by an esterification reaction between the phenolic hydroxyl group-containing compound and the quinone diazide sulphonic acid compound. Known methods of synthesis can be used for this purpose.
The amount of naphthoquinone diazide compound added is preferably from 1 to 50 parts by weight and preferably 3 to 40 parts by weight per 100 parts by weight of polymer.
Again, where required, with the objective of enhancing the application characteristics between the photosensitive resin precursor composition and the substrate, there may be incorporated surfactants, esters such as ethyl lactate and propylene glycol monomethyl ether acetate, alcohols such as ethanol, ketones such as cyclohexanone and methyl isobutyl ketone, and ethers such as tetrahydrofuran and dioxane. Again, there can also be added inorganic particles such as silicon dioxide and titanium dioxide, or powders such as polyimides.
Furthermore, for the purposes of enhancing the adhesion to the silicon wafer or other underlying substrate, there may be added from 0.5 to 10 wt % of silane coupling agent, titanium chelate agent or the like to the photosensitive resin precursor composition varnish, or the underlying substrate can be treated with a chemical of this kind.
Where added to the varnish, there is added the silane coupling agent such as methyl methacryloxy-dimethoxysilane, 3-aminopropyltrimethoxysilane or (vinyltrimethoxysilane), or the titanium chelate agent or aluminium chelate agent, in an amount lying in the range from 0.5 to 10 wt % in terms of the polymer in the varnish.
In the case where the substrate is treated, surface treatment is carried out using a solution in which there is dissolved from 0.5 to 20 wt % of the aforesaid coupling agent in a solvent such as isopropanol, ethanol, methanol, water, tetrahydrofuran, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, ethyl lactate or diethyl adipate, by means of spin coating, immersion, spraying or vapour treatment, etc. Depending of the circumstances, reaction between the substrate and the aforesaid coupling agent is promoted by subsequent heating at a temperature of from 50xc2x0 C. to 300xc2x0 C.
Next, the method of forming a heat-resistant resin pattern using the photosensitive resin precursor composition of the present invention is explained.
The photosensitive resin precursor composition is applied to the substrate. Examples of the substrate employed are silicon wafers, ceramics, gallium arsenide and the like, but there is no restriction thereto. As examples of the application method, there are methods such as rotary coating using a spinner, spray application, roll coating and the like. Again, while the coating thickness will vary with the application method, the solids concentration of the composition and its viscosity, etc, normally application is performed such that the film thickness after drying is from 0.1 to 150 xcexcm.
Next, the substrate on which the photosensitive resin precursor composition has been applied is dried, and a photosensitive resin precursor composition coating obtained. The drying is carried out in the range 50xc2x0 to 150xc2x0 for from 1 minute to several hours, using an oven, a hot plate, infrared radiation or the like.
Next, this photosensitive resin precursor composition coating is exposed to actinic radiation through a mask which has the desired pattern. As examples of the actinic radiation used for the exposure, there are ultraviolet radiation, visible light, an electron beam, X rays and the like but, in the present invention, the use of the mercury lamp i-line (365 nm), h-line (405 nm) or g-line (436 nm) is preferred.
To form the heat-resistant resin pattern, following exposure the exposed regions are eliminated, using a developer. Preferred examples of the developer are aqueous tetramethylammonium solutions, and aqueous solutions of compounds which exhibit alkalinity such as diethanolamine, diethylaminoethanol, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, triethylamine, diethylamine, methylamine, dimethylamine, dimethylaminoethyl acetate, dimethylaminoethanol, dimethylaminoethyl methacrylate, cyclohexylamine, ethylenediamine, hexamethylene diamine and the like. Again, depending on the circumstances, there may be added, to these aqueous alkali solutions, a solvent such as a polar solvent like N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, xcex3-butyrolactone or dimethylacrylamide, an alcohol such as methanol, ethanol or isopropanol, an ester such as ethyl lactate or propylene glycol monomethyl ether acetate, or a ketone such as cyclopentanone, cyclohexanone, isobutyl ketone or methyl isobutyl ketone, or a combination of such solvents. Following the developing, a rinsing treatment is carried out with water. Here too, the treatment may be carried out with the addition, to the water, of an alcohol such as ethanol or isopropyl alcohol, an ester such as ethyl lactate or propylene glycol monomethyl ether acetate, or the like.
After the development, there is applied a temperature in the range 200-500xc2x0, to effect conversion to the heat-resistant resin coating. This heat treatment is carried out for from 5 minutes to 5 hours, either by selection of temperatures and raising the temperature in stages, or by selecting a temperature range and raising the temperature continuously. As an example, the heat treatment is carried out for periods of 30 minutes at 130xc2x0 C., 200xc2x0 C. and 350xc2x0 C. Alternatively, there is the method of raising the temperature linearly over 2 hours from room temperature to 400xc2x0 C.
The heat-resistant resin coating formed from the photosensitive resin precursor composition of the present invention is used in applications such as semiconductor passivation films, semiconductor element protective films and the layer insulation for multilayer circuits for high density mounting.